Bracket angle adjustment mechanism

ABSTRACT

Disclosed is a bracket angle adjustment mechanism adapted to reduce shock to be given to a wedge member, based on an improved wedge shape. The bracket angle adjustment mechanism comprises a pair of wedge members ( 16 A,  16 B). In each of the wedge members ( 16 A,  16 B), an arc-shaped outer surface ( 16   a ) has a diameter slightly less than that of an arc-shaped inner peripheral surface of a large-diameter hole ( 14   c ) of an external-tooth gear ( 14 ), and an arc-shaped inner surface has a diameter slightly greater than that of an arc-shaped outer peripheral surface of a small-diameter shank ( 15   c ) of an internal-tooth gear ( 15 ). The arc-shaped inner surface ( 16   b ) has a circumferential length approximately equal or greater than that of the arc-shaped outer surface ( 16   a ).

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a bracket angle adjustment mechanism.

2. Description of the Related Art

Heretofore, there has been known one type of bracket angle adjustmentmechanism. For example, in a vehicle seat assembly 1 as shown in FIGS.17A to 17C, the bracket angle adjustment mechanism comprises a firstbracket 4 fixed to a seat cushion 2, and a second bracket 5 fixed to aseat back 3, wherein a handle 7 fixed to a control shaft 6 is manuallyrotated clockwise or counterclockwise to adjust an angle of the secondbracket 5 relative to the first bracket 4, i.e. a frontward/rearwardreclining angle of the seat back 3 (see, for example, Japanese PatentPublication No. 63-47443: Patent Publication 1).

More specifically, the first bracket 4 includes an external-tooth gear 4a, and the second bracket 5 includes an internal-tooth gear 5 a whichhas a larger number of teeth than that of the external-tooth gear 4 a.The control shaft 6 has an inward end supported by a central hole 5 b ofthe second bracket 5.

The bracket angle adjustment mechanism further includes a pair of wedgemembers 11A, 11B and a spring member 12. The pair of wedge members 11A,11B are fitted in an eccentric space 10 which is defined between aninner peripheral surface of a large-diameter hole 4 a formed in acentral region of the external-tooth gear 4 a and an outer peripheralsurface of a small-diameter shank 9 a integral with or constituting acentral portion of the internal-tooth gear 5 a (in this conventionalexample, the small-diameter shank 9 a corresponds to a givencircumferential portion 9 a of a follower disk 9 fixed to the controlshaft 6), when respective portions of the external-tooth gear 4 a andthe internal-tooth gear 5 a are engaged with one another. The springmember 12 is interposed between the pair of wedge members 11A, 11B inthe eccentric space to apply a biasing force to each of the wedgemembers 11A, 11B in a wedging direction, i.e. in a direction allowingeach of the wedge members 11A, 11B to be wedged between the innerperipheral surface of the large-diameter central hole 4 a and the outerperipheral surface of the small-diameter central shank 9 a. The controlshaft 6 is adapted to move a wedged-state releasing portion (whichcorresponds to a follower protrusion 9 b formed in the follower disk 9)located between respective wedging ends of the wedge members 11A, 11B.In FIG. 17C, the reference numeral 13 indicates a cover plate fixed tothe second bracket 5. The cover plate 13 extends to cover theexternal-tooth gear 4 a of the first bracket 4, and has a bearingportion 13 a supporting an outward portion of the control shaft 13 a.

In an operation for adjusting an angle of the second bracket 5 relativeto the first bracket 4, i.e. a frontward/rearward reclining angle of theseat back 3, the handle 7 is manually rotated to rotate the controlshaft 6. In conjunction with the rotation of the control shaft 6, thewedged-state releasing portion 9 b is rotated to move the pair of wedgemembers 11A, 11B together with the spring member 12 circularly in theeccentric space 10, so that the small-diameter shank 9 a iseccentrically moved relative to the large-diameter hole 4 b to allow anengagement position of the internal-tooth gear 5 a relative to theexternal-tooth gear 4 a to be changed.

In connection with this type of bracket angle adjustment mechanism, thefollowing technique as shown in FIGS. 18A and 18B has also been known.Each of a pair of wedge members 11A, 11B has an outer (arc-shaped outersurface) radius R which is set to be equal to an inner (inner peripheralsurface) radius R of a large-diameter hole 4 b of an external-tooth gear4 a, and each of the wedge members 11A, 11B has an inner (arch-shapedinner surface) radius “r” set to be equal to an outer (outer peripheralsurface) radius r of a small-diameter shank 9 a of an internal-toothgear 5 a. An eccentric distance “ex” between respective centers of theouter radius R and the inner radius “r” in each of wedge members 11A,11B is set to be slightly greater than an eccentric distance “ez”between respective centers of the inner radius R of the large-diameterhole 4 b of the external-tooth gear 4 a and the outer radius “r” of thesmall-diameter shank 9 a of the internal-tooth gear 5 a (see JapanesePatent Publication No. 03-237904: Patent Publication 2).

In the bracket angle adjustment mechanism as disclosed in the PatentPublications 1 and 2, there remain much needs to be improved. As one ofthe needs, it is desired to reduce shock to be given to either one ofthe wedge members 11A, 11B just after the internal-tooth gear 5 a isrotated by a load from the seat back 3.

SUMMARY OF THE INVENTION

In view of the above need, it is an object of the present invention toprovide a bracket angle adjustment mechanism which can reduce shock tobe given to a wedge member, based on an improved wedge shape.

According to an aspect of the invention, a bracket angle adjustmentmechanism is provided with one bracket including an external-tooth gear;another bracket including an internal-tooth gear which has a largernumber of internal teeth than that of external teeth of theexternal-tooth gear; a pair of wedge members fitted in an eccentricspace which is defined between a large-diameter hole formed in a centralregion of the external-tooth gear and a small-diameter shankconstituting a central portion of the internal-tooth gear, in a statewhen the external-tooth gear and the internal-tooth gear are partlyengaged with one another; a spring member applying a biasing force toeach of the pair of wedge members in a wedging direction; and awedged-state release member disposed between respectivewedging-directional leading edges of the pair of wedge members. Thewedged-state release member is operable, when rotated by a control shaftassociated therewith, to move the pair of wedge members together withthe spring member in a wedged-state release direction circularly in theeccentric space, whereby the small-diameter shank is eccentrically movedrelative to the large-diameter hole to allow an engagement position ofthe internal-tooth gear relative to the external-tooth gear to bechanged so as to adjust an angle of the second bracket relative to thefirst bracket. Each of the pair of wedge members has an inner surfaceand an outer surface each formed into an arc-shape capable of reducingshock to be given to the wedge member.

These and other objects, features, aspects, and advantages of thepresent invention will become more apparent from the following detaileddescription of the preferred embodiments/examples with reference to theaccompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is an exploded perspective view showing a bracket angleadjustment mechanism according to one embodiment of the presentinvention, wherein the mechanism is applied to a vehicle seat assembly.

FIG. 2 is an exploded perspective view showing the bracket angleadjustment mechanism in FIG. 1, when viewed from the side of an outersurface of a second bracket thereof.

FIG. 3 is an exploded perspective view showing the bracket angleadjustment mechanism in FIG. 1, when viewed from the side of an outersurface of a first bracket thereof.

FIG. 4 illustrates a gear unit of the bracket angle adjustment mechanismin FIG. 1, wherein FIG. 4A is a perspective view showing the gear unittogether with the first bracket, and FIG. 4B is an enlarged perspectiveview showing the gear unit.

FIG. 5 illustrates the gear unit in FIG. 4, wherein FIG. 5A is a topplan view, and FIG. 5B is a front plan view.

FIG. 6 illustrates the gear unit in FIG. 5, wherein FIG. 6A is asectional view taken along the line A-A in FIG. 5B, and FIG. 6B is asectional view taken along the line B-B in FIG. 5B.

FIG. 7 is a sectional view taken along the line C-C in FIG. 8.

FIG. 8 is a vertical sectional view showing the bracket angle adjustmentmechanism in FIG. 1.

FIG. 9 illustrates a wedged-state release member of the bracket angleadjustment mechanism in FIG. 1, wherein FIG. 9A is a front view, andFIG. 9B is a side view.

FIG. 10 illustrates a part of teeth in the bracket angle adjustmentmechanism in FIG. 1, wherein FIG. 10A is an enlarged view showinginternal teeth, and FIG. 10B is an enlarged view showing external teeth.

FIG. 11 illustrates a state of tooth engagement, wherein FIG. 11A is anenlarged view showing an engagement state of the internal and externalteeth in the bracket angle adjustment mechanism in FIG. 1, and FIG. 11Bis an enlarged view showing an engagement state of internal and externalteeth in a conventional bracket angle adjustment mechanism.

FIG. 12 illustrates internal-tooth and external-tooth gears in thebracket angle adjustment mechanism in FIG. 1, wherein FIG. 12A is afront view showing an engagement state thereof, and FIG. 12B is aschematic diagram showing respective reference circles of the internalteeth and external teeth thereof.

FIG. 13 is a front view showing a wedge member of the bracket angleadjustment mechanism in FIG. 1, in the state when no load acts on a seatback of the vehicle seat assembly.

FIG. 14 is a front view showing the wedge member, in the state when aload acts on the seat back.

FIG. 15 illustrates one modification of a wedge member, wherein FIG. 15Ais a front view showing the wedge member in a normal position, and FIG.15B is a front view showing the wedge member in a wedged position.

FIG. 16 illustrates the wedge member in FIG. 15 and a wedged-staterelease member, wherein FIG. 16A is a front views showing them in anormal position, and FIG. 16B is a front views showing them in anon-wedged position.

FIG. 17 illustrates a conventional bracket angle adjustment mechanism,wherein FIG. 17A is a perspective view showing a vehicle sheet assemblyequipped therewith, and FIGS. 17B and 17C are, respectively, a partiallysectional front view and a sectional side view showing the conventionalbracket angle adjustment mechanism.

FIG. 18 illustrates a conventional bracket angle adjustment mechanism,wherein FIG. 18A is a front view showing an eccentric space, and FIG.18B is a front view of a wedge member.

FIG. 19 is an explanatory front view of an operation of a wedge memberin a conventional bracket angle adjustment mechanism.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference to the drawings, a best mode for carrying out the presentinvention will now be described. In the related figures,structurally/functionally the same element or component as that of theconventional examples in FIG. 17 to 19 is defined by the same referencenumeral, and its detailed description will be omitted.

A bracket angle adjustment mechanism according to one embodiment of thepresent invention is incorporated in a vehicle seat assembly 1 having aseat cushion 2 and a seat back 3. As shown in FIGS. 1 to 3 and FIG. 8,the bracket angle adjustment mechanism comprises a first bracket 4 whichis fixed to the seat cushion 2 using a bolt (not shown) penetratingthrough each of two bolt holes 4 d formed in the first bracket 4, and asecond bracket 5 which is fixed to the seat back 3 using a bolt (notshown) penetrating through each of two bolt holes 4 d formed in thesecond bracket 5. The bracket angle adjustment mechanism is designed toadjust an angle of the second bracket 5 relative to the first bracket 4,i.e. a frontward/rearward inclining angle of the seat back 3 relative tothe seat cushion 2, according to rotation of a control shaft 20 inconjunction with a clockwise/counterclockwise rotation of a handle 7fixed thereto. In this embodiment, the first and second brackets 4, 5and after-mentioned associated components, such as a gear unit U, arefixed to either one of opposite lateral sides of the seat assembly 1.

The bracket angle adjustment mechanism includes an external-tooth gear14 and an internal-tooth gear 15. The external-tooth gear 14 isintegrally formed in a first disk-shaped plate member by partly pressingan outer surface of the first plate member inward in such a manner as toallow an inner surface thereof to have a convex portion with a pluralityof external teeth. The internal-tooth gear 15 is integrally formed in asecond disk-shaped plate member by partly pressing an inner surface ofthe second plate member outward in such a manner as to allow an outersurface thereof to have a concave portion with a plurality of internalteeth. The external-tooth gear 14 and the internal-tooth gear 15 areassembled together as an after-mentioned gear unit U. Then, theexternal-tooth gear 14 is fixed to the first bracket 4, for example, bywelding after a plurality (eight in this embodiment) of protrusionsformed in the outside surface of the external-tooth gear 14 is fittedinto a plurality of corresponding positioning holes formed in the firstbracket 4. Further, the internal-tooth gear 15 is fixed to the secondbracket 5, for example, by welding after a plurality (eight in thisembodiment) of protrusions formed in the outside surface of theinternal-tooth gear 15 is fitted into a plurality of correspondingpositioning holes formed in the second bracket 5. Alternatively, as withthe conventional bracket angle adjustment mechanism, the external-toothgear 14 may be integrally formed in the first bracket 4 by partlypressing an outer surface of the first bracket 4 inward in such a manneras to allow an inner surface thereof to have a convex portion with aplurality of external teeth, and the internal-tooth gear 15 mayintegrally formed in the second bracket 5 by partly pressing an innersurface of the second bracket 5 outward in such a manner as to allow anouter surface thereof to have a concave portion with a plurality ofinternal teeth.

The internal teeth 15 b of the internal-tooth gear 15 are formed in anumber (fifty in this embodiment) greater than that (forty nine in thisembodiment) of the external teeth 14 b of the external-tooth gear 14.Each shape of the external teeth 14 b of the external-tooth gear 14 andthe internal teeth 15 b of the internal-tooth gear 15 will be describedin detail later with reference to FIGS. 10 and 11.

The external-tooth gear 14 has a central region formed as alarge-diameter hole 14 c, and the internal-tooth gear 15 has a centralregion formed as a hollow small-diameter shank 15 c protruding into thelarge-diameter hole 14 c of the external-tooth gear 14. The firstbracket 4 is formed with a hole 4 e corresponding to the large-diameterhole 14 c of the external-tooth gear 14, and the second bracket 5 isformed with a hole 5 e corresponding to the small-diameter shank 15 c ofthe internal-tooth gear 15.

The bracket angle adjustment mechanism includes a ring-shaped retainermember 22 fitted on an outer peripheral surface of the first platemember having the external-tooth gear 14. The ring-shaped retainermember 22 has an outer peripheral portion formed as a plurality (twelvein this embodiment) of pawls 22 a. In the assembling process of the gearunit U, these pawls 22 a are engaged with a plurality of correspondingcutout portions formed in an outer peripheral surface of the secondplate member having the internal-tooth gear 15, and then folded downwardin a crimping manner, so that the external-tooth gear 14 and theinternal-tooth gear 15 are assembled together as the gear unit U wherethe external teeth 14 b of the external-tooth gear 14 and the internalteeth 15 b of the internal-tooth gear 15 are partly engaged with eachother while allowing a relative movement between the external-tooth gear14 and the internal-tooth gear 15, as shown in FIGS. 5 and 6. While thering-shaped retainer member 22 in this embodiment is designed tocrimpingly hold the external-tooth gear 14 from the side of theinternal-tooth gear 15, it may be designed to crimpingly hold theinternal-tooth gear 15 from the side of the external-tooth gear 14.Further, in place of the ring-shaped retainer member 22, theexternal-tooth gear 14 and the internal-tooth gear 15 may be fastenedtogether using a presser member fixed to either one of the first andsecond brackets 4, 5 by welding or riveting.

The bracket angle adjustment mechanism further includes a pair of wedgemembers 16A, 16B, a spring member 18 and a wedged-state release member19. As shown in FIG. 4, after the external-tooth gear 14 and theinternal-tooth gear 15 are assembled together as the gear unit U usingthe ring-shaped retainer member 22, these components are incorporatedinto an after-mentioned eccentric space 10 etc., from a large-diameteropening 22 b of the ring-shaped retainer member 22. Specifically, thespring member 18 has an outer shape or outer dimensions allowing forbeing housed in an inner space of the wedged-state release member 19. Asshown in FIG. 8, when the external-tooth gear 14 is fixed to the firstbracket 4, for example, by welding after fitting the protrusions 14 a ofthe external-tooth gear 14 into the positioning holes 4 c of the firstbracket 4, the wedged-state release member 19 is pressed by a concaveportion 4 a surrounding the hole 4 e of the first bracket 4, and therebykept from dropping out of the large-diameter hole 14 c.

As specifically shown in FIGS. 7 and 8, when the external teeth 14 b ofthe external-tooth gear 14 and the internal teeth 15 b of theinternal-tooth gear 15 are partly engaged with each other, an eccentricspace 10 is defined between an inner peripheral surface of thelarge-diameter hole 14 c of the external-tooth gear 14 and an outerperipheral surface of the small-diameter shank 15 c of theinternal-tooth gear 15. The pair of wedge members 16A, 16B are fittedinto this eccentric space 10.

The large-diameter hole 14 c of the external-tooth gear 14 is formed tohave a hole length equal to a thickness of the first plate member, andeach of the wedge members 16A, 16B is also formed to have a thicknessequal to the thickness of the first plate member.

In one of conventional bracket angle adjustment mechanisms, aring-shaped member having a length greater than the thickness of thefirst plate member is additionally fitted in the inner surface of thelarge-diameter hole 14 c so as to allow the large-diameter hole 14 c ofthe external-tooth gear 14 to have a hole length greater than thethickness of the first plate member, and each of the wedge members 16A,16B is formed to have a thickness greater than the thickness of thefirst plate member. While this technique is intended to increase thethickness of each of the wedge members 16A, 16B so as to provide anincreased contact surface with the inner peripheral surface of thelarge-diameter hole 14 c and the outer peripheral surface of thesmall-diameter shank 15 c, the ring-shaped member will undesirablyprotrude beyond the thickness of the first plate member to causeincrease in the entire thickness of the bracket angle adjustmentmechanism.

In contrast, the above structure in this embodiment, where thelarge-diameter hole 14 c of the external-tooth gear 14 is formed to havea hole length equal to a thickness of the first plate member, and eachof the wedge members 16A, 16B is also formed to have a thickness equalto the thickness of the first plate member, makes it possible to omitthe ring-shaped member protruding beyond the thickness of the firstplate member, so as to reduce the entire thickness of the bracket angleadjustment mechanism. Further, as measures for increasing a contactsurface of each of the wedge members 16A, 16B relative to the innerperipheral surface of the large-diameter hole 14 c and the outerperipheral surface of the small-diameter shank 15 c, each of the wedgemembers, 16A, 16B may be formed to increase each circumferential lengthof an arc-shaped outer surface 16 a and an arc-shaped inner surface 16a, as described in detail with reference to FIG. 15.

Each of the wedge members 16A, 16B is formed to have an arc-shaped outersurface 16 a approximately along the arc-shaped inner peripheral surfaceof the large-diameter hole 14 c of the external-tooth gear 14, and anarc-shaped inner surface 16 b approximately along the arc-shaped outerperipheral surface of the small-diameter shank 15 c of theinternal-tooth gear 15. Each of the wedge members 16A, 16B is alsoformed in a wedge shape which is gradually increased in width in adirection from a leading edge to a trailing edge thereof. The respectiveshapes of the arc-shaped outer surface 16 a and the arc-shaped innersurface 16 b of each of the wedge members 16A, 16B will be described indetail later with reference to FIGS. 13 and 14.

The spring member 18 is formed in an approximately Ω shape having outerdimensions less than that of the inner peripheral surface 14 c of theexternal-tooth gear 14. As shown in FIG. 7, the spring member 18 has oneend 18 a engaged with a concave portion 16 e formed in the trailing edge16 d of one 16A of the wedge members, and the other end 18 b engagedwith a concave portion 16 e formed in the trailing edge 16 d of theother wedge member 16B. Thus, the spring member 18 is operable to applya biasing force to each of the wedge members 16A, 16B in a wedgingdirection f allowing each of the wedge members 16A, 16B to be wedgedbetween the inner peripheral surface of the large-diameter hole 14 c ofthe external-tooth gear 14 and the outer peripheral surface of thesmall-diameter shank 15 c of the internal-tooth gear 15 in the eccentricspace 10.

The wedged-state release member 19 is formed in a bottomed cylindricalshape, and rotatably fitted in the inner peripheral surface of thelarge-diameter hole 14 c of the external-tooth gear 14. As specificallyshown in FIG. 9, the wedged-state release member 19 is formed with aplurality of clearance grooves 19 a, a pair of pressing portions 19 b,and a noncircular hole 19 d in a bottom 19 c thereof. In the state afterthe wedged-state release member 19 is fitted in the large-diameter hole14 c, the clearance grooves 19 a serve as a means to avoid excessiveinterference between the wedged-state release member 19 and the wedgemembers 16A, 16B, and each of the pressing portions 19 b serves as ameans to press a corresponding one of the wedge members 16A, 16B so asto prevent it from rising toward the wedged-state release member 19.Further, the noncircular hole 19 d is engaged with a noncircular portion20 a of an after-mentioned control shaft 20 in a non-rotatable mannerrelative to the wedged-state release member 19.

The wedged-state release member 19 is further formed with an half-roundarc-shaped wedged-state release portion 19 e is located between therespective wedging or leading edges 19 c of the wedge members 16A, 16B.For example, in FIG. 7, when the wedged-state release member 19 isrotated clockwise, one 19 a of opposite edges of the wedged-staterelease portion 19 e is brought into contact with the leading edge 16 cof the wedge member 16A. When the wedged-state release member 19 isrotated counterclockwise, the other edge 19 g of the wedged-staterelease portion 19 e is brought into contact with the leading edge 16 cof the wedge member 16B. The wedged-state release member 19 is rotatablyfitted in the inner peripheral surface 14 c of the external-tooth gear14 through the wedged-state release portion 19 e and an arc-shapedportion 19 h formed in the wedged-state release member 19 at a positionopposed to the wedged-state release portion 19 e.

With Reference to FIG. 8, after inserted from the hole 5 e of the secondbracket 5 fixed to either one of opposite lateral sides of the seatassembly 1, the noncircular portion of the control shaft 20 is insertedthrough a hole 15 e of the small-diameter shank 15 c of theinternal-tooth gear 15 with a sufficient clearance therebetween, andthen engaged with the noncircular portion 19 d of the wedged-staterelease member 19 in a non-rotatable manner relative thereto.

The noncircular portion 20 a is formed at each of opposite ends of thecontrol shaft 20 to allow the control shaft 20 to be rotated inconjunction with the handle 7 and the gear unit U. In this embodiment,the noncircular portion 20 a has an oval shape formed by pressinglydeforming a pipe-like material of the control shaft 20 from both sidesthereof. The noncircular hole 19 d of the wedged-state release member 19is formed in an oval shape conformable to the oval shape of thenoncircular portion 20 a.

While each of the noncircular portion 19 d of the wedged-state releasemember 19 and the noncircular portion 20 a of the control shaft 20 inthis embodiment is formed in an oval shape, it may have any othersuitable noncircular shape, such as a polygonal shape. Further, thecontrol shaft 20 may be entirely formed as the noncircular portion 20 athrough an extrusion process or a drawing process. Instead of engagingthe noncircular portion 19 d of the wedged-state release member 19 withthe noncircular portion 20 a of the control shaft 20 in a non-rotatablemanner relative thereto, a circular-shaped portion of the wedged-staterelease member 19 may be fitted into a circular-shaped hole of thecontrol shaft 20, and then crimpingly joined together in a non-rotatablemanner relative to one another. Alternatively, the wedged-state releasemember 19 and the control shaft 20 may be designed, respectively, tohave a noncircular-shaped shank fixed thereto or formed therein and acorresponding noncircular-shaped hole formed therein. In this case, thenoncircular-shaped shank may be engaged with the noncircular-shaped holein a non-rotatable manner relative to one another. The wedged-staterelease member 19 can be prepared by subjecting a metal plate to a pressforming process, or through a zinc die-casting process, or a plasticmolding process.

In an operation for fixedly attaching the handle 7 to be manuallyrotated, to one end of the control shaft 20, a corresponding one of thenoncircular portions 20 a is protruded outward, and inserted into ashaft-receiving portion 7 a (see FIG. 1) formed in the handle 7 in anon-rotatable manner. Alternatively, in a type having no control shaft20, the wedged-state release member 19 may be designed to be rotateddirectly by the handle 7.

When the control shaft 20 (or the wedged-state release member 19) isrotated by an electric motor in place of the handle 7, a device (such asa gear, belt or chain pulley) interlocking with the electric motor maybe attached to an appropriate position of the control shaft 20.

For example, in FIG. 7, when the wedged-state release member 19 isrotated clockwise according to rotation of the control shaft 20 inconjunction with a manual operation of the handle 7, one edge 19 f ofthe wedged-state release member 19 is brought into contact with theleading edge 16 c of the wedge member 16A, to move the wedge member 16Aclockwise so as to loosen the wedged state of the wedge member 16A. Inconjunction with the clockwise movement of the wedge member 16A, thewedge member 16B is also moved clockwise through the spring member 18.

Thus, the pair of wedge members 16A, 16B are moved together with thespring 10 circularly in the eccentric space 10, so that thesmall-diameter shank 15 c of the internal-tooth gear 15 is eccentricallymoved relative to the large-diameter hole 4 b of the external-tooth gear14 to allow an engagement position of the internal teeth 15 a relativeto the external teeth 14 b to be changed (when the handle 7 is manuallyrotated 360 degrees, a wedge members 16A, 16B are moved one round, andan internal-teeth gear 15 is rotated by an angle equivalent to one ofthe external teeth of the external-tooth gear 14). Thus, an angle of thesecond bracket 5 relative to the first bracket 4, i.e. afrontward/rearward reclining angle of the seat back 3, can be adjusted.

As specifically shown in FIG. 10, each of the external teeth 14 b of theexternal-tooth gear 14 is designed such that a half-round shape drawnusing a radius “ra” having a single center defined by a point “a” on thereference circle PC (14) is formed in a region of an addendum T1 or in arange between a reference circle PC (14) and an addendum or tip circleAC (14), and an undercut shape is formed in a region of a dedendum T2 orin a range between the reference circle PC (14) and a dedendum or rootcircle DC (14). The reference circle PC (14) has an arc shape. Thus, inthe strict sense, the region of the addendum T1 in each of the externalteeth 14 b has an approximately half-round shape until the abovehalf-round shape drawn by the radius “ra” comes into contact with thearc of the reference circle PC (14).

Preferably, the undercut shape in the region of the dedendum T2 isformed as an arc shape which is drawn by a radius “rb” in such a manneras to be continuously connected to the root circle DC (14). Thisundercut shape makes it possible to eliminate the risk of formation of astep at a joint between the respective regions of the addendum T1 andthe dedendum T2, so as to provide enhanced strength in the externalteeth 14 b.

Each of the internal teeth 15 b of the internal-tooth gear 15 isdesigned to be formed as an arc shape free of interference with theregion of the half-round addendum T1 in a corresponding one of theexternal teeth 14 b of the external-tooth gear 14. Preferably, the arcshape of the internal tooth 15 b in the internal-tooth gear 15 is formedas a combination of two quarter-round shapes drawn, respectively, usingradii “rb”, “rc” having two centers defined by points “b”, “c” on thereference circle PC (15).

As above, each of the external teeth 14 b of the external-tooth gear 14is designed such that a half-round shape having a single center definedby a point “a” on the reference circle PC (14) is formed in the regionof the addendum T1 or in the range between the reference circle PC (14)and the tip circle AC (14), and an undercut shape is formed in theregion of the dedendum T2 or in the range between the reference circlePC (14) and the root circle DC (14). Further, each of the internal teeth15 b of the internal-tooth gear 15 is designed to be formed as an arcshape free of interference with the region of the half-round addendumT1.

According to the above shapes, as shown in FIG. 11A, when theexternal-tooth gear 14 is rotated counterclockwise R, a load F of theexternal tooth 14 b having a half-round-shaped region in the addendum T1constantly acts on the arc-shaped internal tooth 15 b at a right anglein a rotation direction. Thus, as compared with a pressure angle θ′between the external and internal teeth 4 a, 5 a with a conventionalinvolute tooth profile as shown in FIG. 111B, a pressure angle θ betweenthe external and internal teeth 14 b, 15 b becomes smaller. Thisprovides enhanced transmission efficiency to allow an operating forcefor rotating the control shaft 20 to be reduced. In addition, ascompared with the conventional pressure angle θ′, the pressure angle θis located on the inward side relative to a tangent line L. This makesit possible to reduce a load acting on the control shaft 20.Furthermore, as shown in FIGS. 12A and 12B, a range W having an interestbetween the reference circle PC (14) of the external teeth 14 b and thereference circle PC (15) of the internal teeth 15 b is created. Thus,the engagement between the external teeth 14 b and the internal teeth 15b becomes deeper in this region.

According to the above bracket angle adjustment mechanism, in anoperation for rotating the control shaft 20 using the handle 7, thehandle 7 can be manually rotated by a smaller operating force.Otherwise, when the control shaft 20 is rotated using an electric pump,the control shaft 20 can be rotated by a lower output power of theelectric motor. This makes it possible to use a smaller/lighter electricmotor.

In addition, the above advantages can be obtained only by changing theshapes of the external teeth 14 b of the external-tooth gear 14 and theinternal teeth 15 b of the internal-tooth gear 15. Thus, the bracketangle adjustment mechanism can be produced in a significantly simplifiedstructure at a low cost.

As specifically shown in FIG. 13, each of the pair of wedge members 16A,16B in the above embodiment has an arc-shaped outer surface 16 a havinga diameter slightly less than that of the arc-shaped inner peripheralsurface of the large-diameter hole 14 c of the external-tooth gear 14,and an arc-shaped inner surface 16 b having a diameter slightly greaterthan that of the arc-shaped outer peripheral surface of thesmall-diameter shank 15 c of the internal-tooth gear 15.

FIG. 13 shows a state when no load acts on the seat back 3 (secondbracket 5). The bracket angle adjustment mechanism according to thisembodiment is designed such that, in this state, a line K connectingbetween an internal-tooth receiving point “a” where the arc-shaped innersurface 16 b of the wedge member 16B comes into contact with thearc-shaped outer peripheral surface of the small-diameter shank 15 c ofthe internal-tooth gear 15, and an external-tooth receiving point “b”where the arc-shaped outer surface 16 a of the wedge member 16B comesinto contact with the arc-shaped inner peripheral surface of thelarge-diameter hole 14 c of the external-tooth gear 14, is locatedoutward or offset relative to each of a gear center P2 of theexternal-tooth gear 14 and a gear center P1 of the internal-tooth gear15. The line K is spaced apart from the gear center P1 by a distance“j”, and an intersecting point “q” between the line K and a line Iextending from the gear center P1, in the distance “j”, corresponds to aforce application point or action point of the internal-tooth receivingpoint “a” and the external-tooth receiving point “b” of the wedge member16B. In FIG. 13, P3 indicates a center of the arc-shaped outer surface16 a of the wedge member 16B, and P4 indicates a center of thearc-shaped inner surface 16 b of the wedge member 16B. Although notshown herein, the wedge member 16A has the same effects as those of thewedge member 16B as well as the following effects.

As shown in FIG. 14, when a load F is imposed on the second bracket 5from the seat back 3 clockwise, the load F acts on the small-diametershank 15 c of the internal-tooth gear 15, on the basis of an engagementpoint between the internal teeth 15 b of the internal-tooth gear 15 andthe external teeth 14 b of the external-tooth gear 14. When the load Fis received at the internal-tooth receiving point A, and transmitted tothe external-tooth receiving point B through the wedge member 16B, theline K connecting between the internal-tooth receiving point A and theexternal-tooth receiving point B is located outward relative to the gearcenter P2 of the external-tooth gear 14 and the gear center P1 of theinternal-tooth gear 15. Thus, the distance “j” is increased to adistance “J”, and the action point “q” is moved to an action point “Q”,so that the wedge member 16B receives a turning force (see the arrow H)around the external-tooth receiving point B.

Thus, a portion of the arc-shaped outer surface 16 a of the wedge member16B ranging from the external-tooth receiving point B to the trailingedge thereof strongly bites into or contacts the arc-shaped innerperipheral surface of the large-diameter hole 14 c of the external-toothgear 14, and a portion of the arch-shaped inner surface 16 b of thewedge member 16B ranging from the internal-tooth receiving point A tothe leading edge thereof strongly contacts the arc-shaped outerperipheral surface of the small-diameter shank 15 c of theinternal-tooth gear 15. In this manner, even if the load F is imposed onthe second bracket 5 from the seat back 3, the wedge member 16B is urgedin a biting or contact direction to reduce shock to be given to thewedge member 16B, so as to prevent the seat back 3 from being reclined.The same operation and effect as those described above can also beobtained when a counterclockwise load F is imposed on the on the secondbracket 5 from the seat back 3.

In addition, a force causing release of the biting or wedged state isreduced. This makes it possible to use a smaller spring with a lowerspring or biasing force as the spring member 18, and thereby allow thespring member 18 to have outer dimensions for being adequately housed inan inner space of the large-diameter hole 14 c of the external-toothgear 14. The wedge members 16A, 16B can also be reduced in size, such aslength.

In this connection, the following technique as shown in FIG. 19 has alsobeen known. Each of a pair of wedge members 11A, 11B has an outer(arc-shaped outer surface) radius R which is set to be equal to an inner(inner peripheral surface) radius R of a large-diameter hole 4 b of anexternal-tooth gear 4 a, and each of the wedge members 11A, 11B has aninner (arch-shaped inner surface) radius “r” set to be slightly greaterthan an outer (outer peripheral surface) radius r of a small-diametershank 9 a of an internal-tooth gear 5 a.

In this conventional technique, an outer surface (arc-shaped outersurface) in each of the wedge members 11A, 11B comes into contact withan inner surface (inner peripheral surface) of the large-diameter hole 4b of the external-tooth gear 4 a in its entirety, and therefore noinclination occurs in the wedge members 11A, 11B. Further, a contactpoint or area is narrow because the inner (arch-shaped inner surface)radius “r” in each of the wedge members 11A, 11B is slightly greaterthan the outer (outer peripheral surface) radius r of the small-diametershank 9 a of the internal-tooth gear 5 a. Thus, when a counterclockwiseload F is imposed on the second bracket 2 from the seat back 3, the loadF will act on the small-diameter shank 9 a of the internal-tooth gear 5a. Then, when the load F is received at the contact area D, the wedgemember 11A receives a force acting in a direction causing relaxation orrelease of the biting or wedged state, and the seat back 3 is likely tobe reclined. This problem also occurs when a clockwise load F is imposedon the second bracket 2 from the seat back 3.

In the above embodiment, each of the wedge members 16A, 16B has thearc-shaped outer surface 16 a having a diameter slightly less than thatof the arc-shaped inner peripheral surface of the large-diameter hole 14c of the external-tooth gear 14, and the arc-shaped inner surface 16 bhaving a diameter slightly greater than that of the arc-shaped outerperipheral surface of the small-diameter shank 15 c of theinternal-tooth gear 15. Thus, the arc-shaped outer surfaces 16 a and thearc-shaped outer surfaces 16 b of the wedge members 16A, 16B are alwaysmoved circularly in the eccentric space 10 with a small clearance. Thisallows variations in the concentric space 10 due to vitiations inmachining accuracy of an arc-shaped inner peripheral surface of thelarge-diameter hole 14 c of the external-tooth gear 14 and an arc-shapedouter peripheral surface of the small-diameter shank 15 c of theinternal-tooth gear 15, to be absorbed by the wedge members 16A, 16B.

In the above embodiment, as to respective circumferential lengths of thearc-shaped outer surface 16 a and the arc-shaped inner surface 16 b ineach of the wedge members 16A, 16B, the arc-shaped outer surface 16 a islonger, and the arc-shaped inner surface 16 b is shorter (small inarea). This conventional setting of circumferential lengths involves therisk of concentration of load in the small-diameter shank 15 c of theinternal-tooth gear 15 due to increase in surface pressure of thearc-shaped inner surface 16 b having a shorter length. Specifically,referring to FIG. 14, the circumferential length of the arc-shaped innersurface 16 b in each of the wedge members 16A, 16B is about ⅛ of thecircumferential length of the small-diameter shank 15 c.

With a focus on this point, as shown in FIG. 15, the arc-shaped innersurface 16 b in each of the wedge members 16A, 16B is designed toincrease a circumferential length in such a manner that it is to beabout ⅓ of the circumferential length of the small-diameter shank 15 c.While the arc-shaped inner surface 16 b in FIG. 15 has a circumferentiallength greater than that of the arc-shaped outer surfaces 16 a (thecircumferential length of the arc-shaped inner surface 16 b is about ¼of the circumferential length of the small-diameter shank 15 c), it mayhave approximately the same circumferential length as that of thesmall-diameter shank 15 c.

Further, in each of the wedge members 16A, 16B, a cutout portion 16 f isformed in a portion of the arc-shaped outer surfaces 16 a on the side ofthe leading edge 16 c, and the wedged-state release member 19 is incontact with the cutout portion 16 f.

FIG. 15A shows a state when no load acts on the seat back 3 (secondbracket 5). In this state, a line K connecting between an internal-toothreceiving point “a” where the arc-shaped inner surface 16 b of the wedgemember 16B comes into contact with the arc-shaped outer peripheralsurface of the small-diameter shank 15 c of the internal-tooth gear 15,and an external-tooth receiving point “b” where the arc-shaped outersurface 16 a of the wedge member 16B comes into contact with thearc-shaped inner peripheral surface of the large-diameter hole 14 c ofthe external-tooth gear 14, is located outward or offset relative toeach of a gear center P2 of the external-tooth gear 14 and a gear centerP1 of the internal-tooth gear 15. The line K is spaced apart from thegear center P1 by a distance “j”, and an intersecting point “q” betweenthe line K and a line I extending from the gear center P1, in thedistance “j”, corresponds to an action point of the internal-toothreceiving point “a” and the external-tooth receiving point “b” of thewedge member 16B. In FIG. 15A, P3 indicates a center of the arc-shapedouter surface 16 a of the wedge member 16B, and P4 indicates a center ofthe arc-shaped inner surface 16 b of the wedge member 16B. Although notshown herein, the wedge member 16A has the same effects as those of thewedge member 16B as well as the following effects.

As shown in FIG. 15B, when a load F is imposed on the second bracket 5from the seat back 3 clockwise, the load F acts on the small-diametershank 15 c of the internal-tooth gear 15, on the basis of an engagementpoint between the internal teeth 15 b of the internal-tooth gear 15 andthe external teeth 14 b of the external-tooth gear 14. When the load Fis received at the internal-tooth receiving point A, and transmitted tothe external-tooth receiving point B through the wedge member 16B, theline K connecting between the internal-tooth receiving point A and theexternal-tooth receiving point B is located outward relative to the gearcenter P2 of the external-tooth gear 14 and the gear center P1 of theinternal-tooth gear 15. Then, if the distance “j” is reduced to adistance “J” (distance j<J), and the action point q is moved to anaction point Q, the line K connecting between the internal-toothreceiving point A and the external-tooth receiving point B in the wedgemember 16B will be kept at a position located outward relative to thegear center P2 of the external-tooth gear 14 and the gear center P1 ofthe internal-tooth gear 15, so that the wedge member 16B receives aturning force (see the arrow H) around the external-tooth receivingpoint B.

Thus, a portion of the arc-shaped outer surface 16 a of the wedge member16B ranging from the external-tooth receiving point B to the trailingedge thereof strongly bites into or contacts the arc-shaped innerperipheral surface of the large-diameter hole 14 c of the external-toothgear 14, and a portion of the arch-shaped inner surface 16 b of thewedge member 16B ranging from the internal-tooth receiving point A tothe leading edge thereof strongly contacts the arc-shaped outerperipheral surface of the small-diameter shank 15 c of theinternal-tooth gear 15. In this manner, even if the load F is imposed onthe second bracket 5 from the seat back 3, the wedge member 16B is urgedin a biting or contact direction to reduce shock to be given to thewedge member 16B, and prevent the seat back 3 from being reclined. Thesame operation and effect as those described above can also be obtainedwhen a counterclockwise load F is imposed on the on the second bracket 5from the seat back 3.

In addition, a force causing release of the biting or wedged state isreduced. This makes it possible to use a smaller spring with a lowerspring or biasing force as the spring member 18, and thereby allow thespring member 18 to have outer dimensions for being adequately housed inan inner space of the large-diameter hole 14 c of the external-toothgear 14.

Further, as to the respective circumferential lengths of the arc-shapedouter surface 16 a and the arc-shaped inner surface 16 b in each of thewedge members 16A, 16B, they are approximately the same, or thearc-shaped inner surface 16 b is relatively longer (approximately thesame or larger in area). Thus, a surface pressure of the arc-shapedinner surface 16 b can be reduced to reduce the risk of concentration ofload in the small-diameter shank 15 c of the internal-tooth gear 15.

As shown in FIGS. 16A and 16B, when the wedged-state release member 19is rotated clockwise (see the arrow), for example, as shown in FIG. 16B,according to rotation of the control shaft 20 in conjunction with amanual operation of the handle 7, one edge 19 f of the wedged-staterelease portion 19 e is brought into contact with the cutout portion 16f of the wedge member 16A, to move the wedge member 16A clockwise so asto loosen the wedged state of the wedge member 16A. In conjunction withthe clockwise movement of the wedge member 16A, the wedge member 16B isalso moved clockwise through the spring member 18. Thus, an angle of thesecond bracket 5 relative to the first bracket 4, i.e. afrontward/rearward reclining angle of the seat back 3, can be adjustedin the same manner as that in the aforementioned embodiment. In theabove operation, the wedged-state release portion 19 e of thewedged-state release member 19 is brought into contact with the cutoutportion 16 f formed in the arc-shaped outer surface 16 a of the wedgemember 16A. That is, the wedged-state release portion 19 e presses aportion of the wedge member 16B located close to the outer surfacethereof, against the aforementioned turning force (see the arrow H), toallow the wedge member to be moved in a direction opposite to that ofthe turning force. Thus, the wedged state of the wedge member can bemore easily relaxed or released.

In the above embodiment, the wedged-state release member 19 is held bythe external-tooth gear 14 in such a manner that the outer peripheralsurface of the wedged-state release member 19 is rotatably fitted in thelarge-diameter hole 14 c formed in the central region of theexternal-tooth gear 14. This allows the wedged-state release member 19to be stably rotated along the large-diameter hole 14 c of theexternal-tooth gear 14 and to be increased in size so as to haveenhanced strength. In addition, this makes it possible to simplify theshape of the wedged-state release member 19 so as to facilitatereduction in production cost.

In the above embodiment, in the state after the wedged-state releasemember 19 is fitted in the large-diameter hole 14 c, the clearancegrooves 19 a can prevent needless interference between the wedged-staterelease member 19 and the wedge members 16A, 16B.

In the above embodiment, the control shaft 20 for selectively rotatingthe wedged-state release member 19 is fixed to the wedged-state releasemember 19 by inserting the noncircular portion (fixing portion) 20 a ofthe control shaft 20 into the noncircular hole 19 d of the wedged-staterelease member 19. Thus, the control shaft 20 is simply inserted intothe hole 15 e of the small-diameter shank 15 c of the internal-toothgear 15 in a non-fitting manner, so that the need for fitting thecylindrical-shaped portion of the wedged-state release member 19 intothe small-diameter shank 15 c of the internal-tooth gear 15 can beeliminated. This makes it possible to increase the wall thickness of thesmall-diameter shank 15 c and the diameter of the control shaft 20 so asto provide enhanced strength thereof. Further, the control shaft 20 canbe fixedly connected to the wedged-state release member 19 simply byinserting the noncircular portion 20 a of the control shaft 20 into thenoncircular hole 19 d of the wedged-state release member 19, without theneed for a spline connection between the cylindrical-shaped portion ofthe wedged-state release member 19 and the control shaft 20. Thus, theinsertion/connection structure can be simplified.

While the bracket angle adjustment mechanism according to the aboveembodiment has been designed to adjust a relative angle between thebrackets 4, 5 related to a reclining function of the vehicle seatassembly 1, it is understood that the present invention may be appliedto any other type of bracket angle adjustment mechanism for adjusting arelative angle between one bracket 4 and the other bracket 5 for use,for example, in a lifter for a vehicle seat 1 or a vehicle power windowapparatus.

As described above, an inventive bracket angle adjustment mechanismcomprises a first bracket including an external-tooth gear, a secondbracket including an internal-tooth gear which has a larger number ofinternal teeth than that of external teeth of the external-tooth gear, apair of wedge members fitted in an eccentric space which is definedbetween a large-diameter hole formed in a central region of theexternal-tooth gear and a small-diameter shank constituting a centralportion of the internal-tooth gear, in a state when the external-toothgear and the internal-tooth gear are partly engaged with one another, aspring member applying a biasing force to each of the pair of wedgemembers in a wedging direction, and a wedged-state release memberdisposed between respective wedging-directional leading edges of thepair of wedge members, the wedged-state release member being operable,when rotated by a control shaft associated therewith, to move the pairof wedge members together with the spring member in a wedged-staterelease direction circularly in the eccentric space, whereby thesmall-diameter shank is eccentrically moved relative to thelarge-diameter hole to allow an engagement position of theinternal-tooth gear relative to the external-tooth gear to be changed soas to adjust an angle of the second bracket relative to the firstbracket. Each of the pair of wedge members has an inner surface and anouter surface each formed into an arc-shape capable of reducing a shockto be given to the wedge member.

In the bracket angle adjustment mechanism, the arc-shaped outer surfaceof each of the pair of wedge members may have a diameter slightly lessthan that of an arc-shaped inner peripheral surface of thelarge-diameter hole of the external-tooth gear, and the arc-shaped innersurface of each of the pair of wedge members may have a diameterslightly greater than that of an arc-shaped outer peripheral surface ofthe small-diameter shank of the internal-tooth gear.

In the bracket angle adjustment mechanism, the arc-shaped inner surfaceof each of the pair of wedge members may have a circumferential lengthapproximately equal or greater than that of the arc-shaped outer surfaceof each of the pair of wedge members.

Further, the arc-shaped outer surface of each of the pair of wedgemembers may have a diameter slightly less than that of an arc-shapedinner peripheral surface of the large-diameter hole of theexternal-tooth gear, and the arc-shaped inner surface of each of thepair of wedge members may have a diameter slightly greater than that ofan arc-shaped outer peripheral surface of the small-diameter shank ofthe internal-tooth gear.

In the bracket angle adjustment mechanism, a line connecting between aninternal-tooth receiving point where the arc-shaped inner surface ofeach of the wedge members comes into contact with an arc-shaped outerperipheral surface of the small-diameter shank of the internal-toothgear, and an external-tooth receiving point where the arc-shaped outersurface of each of the wedge members comes into contact with anarc-shaped inner peripheral surface of the large-diameter hole of theexternal-tooth gear, may be located outward relative to each of a gearcenter of the external-tooth gear and a gear center of theinternal-tooth gear.

In the bracket angle adjustment mechanism, the arc-shaped outer surfaceof each of the wedge members may be formed with a cutout portion. Inthis case, the wedged-state release member may be designed to be broughtinto contact with the cutout portion.

In the bracket angle adjustment mechanism, the large-diameter hole ofthe external-tooth gear may have a hole length equal to a thickness ofthe central region of the external-tooth gear, and each of the wedgemembers may have a thickness equal to that of the central region of theexternal-tooth gear.

In the bracket angle adjustment mechanism, the spring member may have anouter shape allowing for being housed in an inner space of thelarge-diameter hole of the external-tooth gear.

The bracket angle adjustment mechanism may be used with a seat assemblyhaving a seat back and a seat cushion to adjust a frontward/rearwardangle of the seat back relative to the seat cushion, wherein one of thefirst and second brackets is fixed to the seat back, and the otherbracket is fixed to the seat cushion.

With these constructions, each of the pair of wedge members has an innersurface and an outer surface each formed into an arc-shape capable ofreducing a shock to be given to the wedge member. This makes it possibleto reduce the risk of unintended reclining of a seat back. Thearc-shaped outer surface of each of the pair of wedge members may have adiameter slightly less than that of an arc-shaped inner peripheralsurface of the large-diameter hole of the external-tooth gear, and thearc-shaped inner surface of each of the pair of wedge members may have adiameter slightly greater than that of an arc-shaped outer peripheralsurface of the small-diameter shank of the internal-tooth gear. In thiscase, when a load is imposed on the second bracket from the seat back,the load will act on the small-diameter shank of the internal-toothgear, on the basis of an engagement point between the internal teeth andthe external teeth. Then, when the load is received by an innerperipheral surface of each of the wedge member and transmitted to thelarge-diameter hole of the external-tooth gear through an outerperipheral surface of the wedge member, the wedge member receives aturning force in the biting or contact direction.

Thus, the arch-shaped outer surface of the wedge member strongly bitesinto or contacts the arc-shaped inner peripheral surface of thelarge-diameter hole of the external-tooth gear, and the arch-shapedinner surface of the wedge member strongly bites into or contacts thearc-shaped outer peripheral surface of the small-diameter shank of theinternal-tooth gear. In this manner, even if the load is imposed on thesecond bracket from the seat back, the wedge member is urged in a bitingor contact direction to reduce shock to be given to the wedge member,and prevent the seat back from being reclined.

Further, the arc-shaped outer surface of the wedge member may have adiameter slightly less than that of an arc-shaped inner peripheralsurface of the large-diameter hole of the external-tooth gear, and thearc-shaped inner surface of the wedge member may have a diameterslightly greater than that of an arc-shaped outer peripheral surface ofthe small-diameter shank of the internal-tooth gear. In this case, thearc-shaped outer surfaces and the arc-shaped outer surfaces of the wedgemember are always moved circularly in the eccentric space with a smallclearance. This allows variations in the concentric space due tovitiations in machining accuracy of an arc-shaped inner peripheralsurface of the large-diameter hole of the external-tooth gear and anarc-shaped outer peripheral surface of the small-diameter shank of theinternal-tooth gear, to be absorbed by the wedge member.

The arc-shaped inner surface of each of the pair of wedge members mayhave a circumferential length approximately equal or greater than thatof the arc-shaped outer surface of each of the pair of wedge members. Inthis case, for example, when a load is imposed on the second bracketfrom the seat back, the load will act on the small-diameter shank of theinternal-tooth gear, on the basis of an engagement point between theinternal teeth and the external teeth. Then, when the load is receivedby an inner peripheral surface of each of the wedge member andtransmitted to the large-diameter hole of the external-tooth gearthrough an outer peripheral surface of the wedge member, the wedgemember receives a turning force in the biting or contact direction.

In this moment, the arc-shaped outer surface of the wedge memberstrongly contacts the arc-shaped inner peripheral surface of thelarge-diameter hole of the external-tooth gear, and the arc-shaped innersurface of the wedge member strongly contacts the arc-shaped outerperipheral surface of the small-diameter shank of the internal-toothgear, because the respective circumferential lengths of the arc-shapedouter surface and the arc-shaped inner surface of the wedge member areapproximately the same, or the arc-shaped inner surface is relativelylonger (approximately the same or larger in area). Thus, a surfacepressure of the arc-shaped inner surface 16 b can be reduced to reducethe risk of concentration of load in the small-diameter shank 15 c ofthe internal-tooth gear 15. Thus, even if the load is imposed on thesecond bracket from the seat back, the wedge member is urged in a bitingor contact direction to reduce shock to be given to the wedge member,and prevent the seat back 3 from being reclined.

Conventionally, as to respective circumferential lengths of thearc-shaped outer surface and the arc-shaped inner surface in the wedgemember, the arc-shaped inner surface is relatively shorter (small inarea). In this case, there is the risk of concentration of load in thesmall-diameter shank of the internal-tooth gear due to increase insurface pressure of the arc-shaped inner surface. In contrast, when therespective circumferential lengths of the arc-shaped outer surface andthe arc-shaped inner surface of the wedge member are approximately thesame, or the arc-shaped inner surface is relatively longer(approximately the same or larger in area), a surface pressure of thearc-shaped inner surface can be reduced to prevent the risk ofconcentration of load in the small-diameter shank of the internal-toothgear.

This application is based on patent application No. 2004-379691 filed inJapan, the contents of which are hereby incorporated by references.

This invention may be embodied in several forms without departing fromthe spirit of essential characteristics thereof, the present embodimentis therefore illustrative and not restrictive, since the scope of theinvention is defined by the appended claims rather than by thedescription preceding them, and all changes that fall within metes andbounds of the claims, or equivalence of such metes and bounds aretherefore intended to embraced by the claims.

1. A bracket angle adjustment mechanism comprising: a first bracketincluding an external-tooth gear; a second bracket including aninternal-tooth gear which has a larger number of internal teeth thanthat of external teeth of the external-tooth gear; a pair of wedgemembers fitted in an eccentric space which is defined between alarge-diameter hole formed in a central region of the external-toothgear and a small-diameter shank constituting a central portion of theinternal-tooth gear, in a state when the external-tooth gear and theinternal-tooth gear are partly engaged with one another; a spring memberapplying a biasing force to each of the pair of wedge members in awedging direction; and a wedged-state release member disposed betweenrespective wedging-directional leading edges of the pair of wedgemembers, the wedged-state release member being operable, when rotated bya control shaft associated therewith, to move the pair of wedge memberstogether with the spring member in a wedged-state release directioncircularly in the eccentric space, whereby the small-diameter shank iseccentrically moved relative to the large-diameter hole to allow anengagement position of the internal-tooth gear relative to theexternal-tooth gear to be changed so as to adjust an angle of the secondbracket relative to the first bracket, wherein each of the pair of wedgemembers has an inner surface and an outer surface each formed into anarc-shape capable of reducing shock to be given to the wedge; andwherein the arc-shaped outer surface of each of the wedge members isformed with a cutout portion, wherein the wedged-state release member isdesigned to be brought into contact with the cutout portion.
 2. Thebracket angle adjustment mechanism as defined in claim 1, wherein a lineconnecting between an internal-tooth receiving point where thearc-shaped inner surface of each of the wedge members comes into contactwith an arc-shaped outer peripheral surface of the small-diameter shankof the internal-tooth gear, and an external-tooth receiving point wherethe arc-shaped outer surface of each of the wedge members comes intocontact with an arc-shaped inner peripheral surface of thelarge-diameter hole of the external-tooth gear, is located outwardrelative to each of a gear center of the external-tooth gear and a gearcenter of the internal-tooth gear.
 3. The bracket angle adjustmentmechanism as defined in claim 1, wherein: the large-diameter hole of theexternal-tooth gear has a hole depth equal to a thickness of the centralregion of the external-tooth gear; and each of the wedge members has athickness equal to that of the central region of the external-toothgear.
 4. The bracket angle adjustment mechanism as defined in claim 1,which is used with a seat assembly having a seat back and a seat cushionto adjust a frontward/rearward angle of the seat back relative to theseat cushion, wherein one of the first and second brackets is fixed tothe seat back, and the other bracket is fixed to the seat cushion. 5.The bracket angle adjustment mechanism as defined in claim 1, wherein:the arc-shaped outer surface of each of the pair of wedge members has adiameter slightly less than that of an arc-shaped inner peripheralsurface of the large-diameter hole of the external-tooth gear; and thearc-shaped inner surface of each of the pair of wedge members has adiameter slightly greater than that of an arc-shaped outer peripheralsurface of the small-diameter shank of the internal-tooth gear.
 6. Thebracket angle adjustment mechanism as defined in claim 5, wherein a lineconnecting between an internal-tooth receiving point where thearc-shaped inner surface of each of the wedge members comes into contactwith an arc-shaped outer peripheral surface of the small-diameter shankof the internal-tooth gear, and an external-tooth receiving point wherethe arc-shaped outer surface of each of the wedge members comes intocontact with an arc-shaped inner peripheral surface of thelarge-diameter hole of the external-tooth gear, is located outwardrelative to each of a gear center of the external-tooth gear and a gearcenter of the internal-tooth gear.
 7. The bracket angle adjustmentmechanism as defined in claim 5, wherein: the large-diameter hole of theexternal-tooth gear has a hole depth equal to a thickness of the centralregion of the external-tooth gear; and each of the wedge members has athickness equal to that of the central region of the external-toothgear.
 8. The bracket angle adjustment mechanism as defined in claim 5,wherein the spring member has an outer shape allowing for being housedin an inner space of the large-diameter hole of the external-tooth gear.9. The bracket angle adjustment mechanism as defined in claim 5, whichis used with a seat assembly having a seat back and a seat cushion toadjust a frontward/rearward angle of the seat back relative to the seatcushion, wherein one of the first and second brackets is fixed to theseat back, and the other bracket is fixed to the seat cushion.
 10. Thebracket angle adjustment mechanism as defined in claim 1, wherein thearc-shaped inner surface of each of the pair of wedge members has acircumferential length approximately equal or greater than that of thearc-shaped outer surface of each of the pair of wedge members.
 11. Thebracket angle adjustment mechanism as defined in of claim 10, wherein:the arc-shaped outer surface of each of the pair of wedge members has adiameter slightly less than that of an arc-shaped inner peripheralsurface of the large-diameter hole of the external-tooth gear; and thearc-shaped inner surface of each of the pair of wedge members has adiameter slightly greater than that of an arc-shaped outer peripheralsurface of the small-diameter shank of the internal-tooth gear.
 12. Thebracket angle adjustment mechanism as defined in claim 11, wherein aline connecting between an internal-tooth receiving point where thearc-shaped inner surface of each of the wedge members comes into contactwith an arc-shaped outer peripheral surface of the small-diameter shankof the internal-tooth gear, and an external-tooth receiving point wherethe arc-shaped outer surface of each of the wedge members comes intocontact with an arc-shaped inner peripheral surface of thelarge-diameter hole of the external-tooth gear, is located outwardrelative to each of a gear center of the external-tooth gear and a gearcenter of the internal-tooth gear.
 13. The bracket angle adjustmentmechanism as defined in claim 11, wherein: the large-diameter hole ofthe external-tooth gear has a hole depth equal to a thickness of thecentral region of the external-tooth gear; and each of the wedge membershas a thickness equal to that of the central region of theexternal-tooth gear.
 14. The bracket angle adjustment mechanism asdefined in claim 11, wherein the spring member has an outer shapeallowing for being housed in an inner space of the large-diameter holeof the external-tooth gear.
 15. The bracket angle adjustment mechanismas defined in claim 11, which is used with a seat assembly having a seatback and a seat cushion to adjust a frontward/rearward angle of the seatback relative to the seat cushion, wherein one of the first and secondbrackets is fixed to the seat back, and the other bracket is fixed tothe seat cushion.
 16. A bracket angle adjustment mechanism a firstbracket including an external-tooth gear; a second bracket including aninternal-tooth gear which has a larger number of internal teeth thanthat of external teeth of the external-tooth gear; a pair of wedgemembers fitted in an eccentric space which is defined between alarge-diameter hole formed in a central region of the external-toothgear and a small-diameter shank constituting a central portion of theinternal-tooth gear, in a state when the external-tooth gear and theinternal-tooth gear are partly engaged with one another; a spring memberapplying a biasing force to each of the pair of wedge members in awedging direction; and a wedged-state release member disposed betweenrespective wedging-directional leading edges of the pair of wedgemembers, the wedged-state release member being operable, when rotated bya control shaft associated therewith, to move the pair of wedge memberstogether with the spring member in a wedged-state release directioncircularly in the eccentric space, whereby the small-diameter shank iseccentrically moved relative to the large-diameter hole to allow anengagement position of the internal-tooth gear relative to theexternal-tooth gear to be changed so as to adjust an angle of the secondbracket relative to the first bracket, wherein each of the pair of wedgemembers has an inner surface and an outer surface each formed into anarc-shape capable of reducing shock to be given to the wedge member; andwherein the spring member has an outer shape allowing for being housedin an inner space of the large-diameter hole of the external-tooth gear.17. The bracket angle adjustment mechanism as defined in claim 16,wherein the arc-shaped outer surface of each of the wedge members isformed with a cutout portion, wherein the wedged-state release member isdesigned to be brought into contact with the cutout portion.